JPH04157164A - Plasma treating device - Google Patents

Abstract

PURPOSE:To allow the execution of a uniform plasma treatment at a high speed by using plural divided electrodes to constitute the anode grounding electrode side of a pair of the opposed electrodes in the plasma generating chamber of the plasma treating device so that impedance correction can be made for each of the respective divided electrodes. CONSTITUTION:The inside of the plasma generating chamber 1 of the plasma treating device for functional thin films or etching, etc., is evacuated to a reduced pressure from a discharge port 8 and an etching gas, such as CF4, is supplied from a gas supply chamber 7. The anode electrode 2 which is constituted of the cathode electrode 3 imposed with the substrate 5 to be treated and the divided electrodes 2a, 2b disposed to face this electrode and is insulated from each other by a ceramic material 11 is provided in the plasma generating chamber 1. The anode 2a is grounded via a variable capacity capacitor 12 and the anode 2b is directly grounded. The cathode electrode 3 is connected to a grounded high-frequency power source 4 and a matching device 10. A high-frequency voltage is impressed to this electrode to generate plasma. The plasma formed between the cathode electrode 3 and the divided anode electrodes 2a, 2b is uniformized by the presence of the variable capacity capacitor 12 and the substrate 5 is subjected to the uniform etching.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to semiconductor devices, line sensors for image input,
The present invention relates to a plasma processing apparatus suitable for uniform processing in various plasma processing techniques such as functional thin film formation and etching used in manufacturing imaging devices, photovoltaic devices, etc.

□ [Prior Art] Conventionally, amorphous silicon, such as hydrogen atoms and/or halogens, has been used as an electronic component for semiconductor devices, line sensors for human power imaging, imaging devices, photovoltaic devices, and other various electronic devices and optical devices. Various deposited films of amorphous semiconductors such as amorphous silicon compensated with atoms (eg, fluorine, chlorine, etc.) have been proposed, and some of them have been put into practical use.

Furthermore, various dry etching methods using plasma have been proposed as high-definition and high-speed device isolation formation means, and some of them have been put into practical use.

Among these various dry etching methods, the reactive ion etching method (hereinafter referred to as "rRIE method"), in which the etching gas is decomposed by a glow discharge using high frequency, and the generated ion particles are directed in one direction. Anisotropic etching is known, in which ions are accelerated by a potential difference within a sheath and incident on the substrate to be processed, causing a chemical reaction with the semiconductor material on the substrate, and discharging/removing the generated gaseous reactants. In recent years, it has attracted attention as an extremely effective means for forming high-definition elements, and various apparatuses for this purpose have been proposed.

As an apparatus for removing semiconductor materials and the like by the RIE method, one having a configuration typically shown in the schematic cross-sectional view of FIG. 3 is known. In FIG. 3, reference numeral 1 indicates the entire plasma generation chamber formed airtight, and reference numeral 2 indicates a circular anode electrode that is grounded. A circular cathode electrode 3 is connected to the plasma generation chamber and an insulated high frequency power source 4.

5 is a substrate to be processed. 6 is the cathode electrode 3
, and a drive mechanism for rotating the base body 5. Reference numeral 7 denotes an etching gas supply pipe whose one end opens into the plasma generation chamber 1 and whose other end communicates with an etching gas supply source (not shown) via a valve means (not shown). Reference numeral 8 denotes an exhaust pipe having one end open into the plasma generation chamber 1 and the other end equipped with an exhaust valve (not shown) communicating with an exhaust device (not shown). Etching processing using such a conventional RIE plasma processing apparatus is performed, for example, as follows.

That is, the etching gas supply valve (not shown) is closed, the inside of the plasma generation chamber 1 is evacuated from the exhaust port 8, and the internal pressure is reduced to 1. O
X 10-'Torr or less. Next, the gas supply valve is opened and carbon tetrafluoride (hereinafter referred to as CFa) is supplied as an etching gas through the gas discharge hole of the gas supply pipe 7.
is introduced until the pressure within the system reaches 5 x 10-2 Torr. Therefore, the high frequency power supply 4 is energized and the frequency is 13.56 M.
A high frequency of Hz is applied to the cathode electrode 3 to generate plasma, accelerate CF3'' ions within the ion sheath, and make them incident on the substrate 5 on the cathode electrode 3 a-5i, (H, x
) etc. to form gaseous silicon tetrafluoride (hereinafter referred to as SiF).
4), and a-5i, ()I, After processing for a predetermined period of time, supply of etching gas, application of high frequency power, etc. is stopped, and the substrate is carried out of the system to complete the etching processing.

[Problem that the invention is trying to solve]

However, in the conventional parallel plate electrode plasma processing apparatus configured as shown in Figure 's2, between the electrodes,
There is a distribution of high-frequency power applied, and the plasma density tends to be high around the electrode and low at the center. Therefore, depending on the size of the electrode and operating conditions, the ion energy may become non-uniform and the etching distribution within the substrate may become large. For example, electrode diameter 5
Using an RIE device with an electrode distance of 50 m, the system pressure was set to 5 x 10-” Torr, and the high-frequency power was 300 W.
When the amorphous silicon (n+) film deposited on the substrate is etched under the etching condition of F4 gas flow rate of 255 CCM, the etching rate is 200 CCM at the center of the substrate.
The etching distribution becomes larger in the surrounding area, such as 250 people/minute.

An object of the present invention is to provide a plasma processing apparatus having a configuration that prevents the occurrence of processing unevenness in such a plasma processing apparatus and enables uniform and high-speed plasma processing.

[Means to solve the problem]

A plasma processing apparatus of the present invention that achieves the above object is a plasma processing apparatus having a pair of opposing electrodes to which high-frequency power for plasma generation is applied in a plasma generation chamber, the ground electrode (anode) of the pair of opposing electrodes. ) side is composed of a plurality of divided electrodes, and the impedance can be corrected for each divided electrode.

The manner in which the ground (anode) electrodes of a pair of opposing electrodes are divided to form divided electrodes may be appropriately selected depending on the distribution (variation) of plasma density occurring between the electrodes.

For example, when a region of high plasma density and a region of low plasma density are formed between a pair of opposing electrodes, the first electrode portion corresponds to the region of high plasma density and the second electrode portion corresponds to the region of low plasma density. The electrode is divided into two parts, and the impedance of the first electrode part and/or the second electrode part is adjusted to shift the matching of the high frequency power input between the electrodes via these parts, and the first electrode part is divided into two parts. by utilizing a second electrode portion to obtain an effect substantially similar to reducing the applied high frequency power, or by utilizing a second electrode portion to obtain an effect substantially similar to increasing the applied high frequency power. By obtaining these effects, or by obtaining both of these effects at the same time, it is possible to equalize the high frequency power input between these electrodes, thereby making it possible to obtain a uniform plasma density.

In addition, when the plasma density is made uniform by increasing the plasma density in a region with a low plasma density by impedance correction of the divided electrodes, it is possible to increase the plasma processing speed, which has been limited by the region with a low plasma density. Conversely, when equalizing the plasma density by reducing the plasma density in areas with high plasma density by impedance correction of the divided electrodes, if the input high-frequency power is constant, the Although the plasma density is made uniform at a smaller value, by increasing the input high-frequency power, the uniform plasma density is increased and plasma processing at higher speed becomes possible.

The impedance correction of the divided electrodes can be performed by an electric circuit or by adjusting the distance between the divided electrodes, and these may be used in combination.

As an electric circuit for impedance correction, a circuit that controls a capacitance component using a variable capacitor, etc. can be used. Note that the circuit that controls the capacitance component includes:
If necessary, a circuit for controlling the actance component using a coil or the like, a circuit for controlling the resistance component using a resistor, etc. may be combined.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

FIG. 1 is a longitudinal sectional view showing the main parts of a plasma processing apparatus showing a first embodiment of the present invention.

1 is an airtight plasma generation chamber, which is equipped with a vacuum pump (
(not shown) and is exhausted from the exhaust port 8 via a valve (not shown). Reference numeral 2 denotes an anode electrode facing the cathode electrode 3, and as shown in FIG. 3, it is divided into two parts such that the central part is constituted by a divided electrode 2b, and the peripheral part surrounding the divided electrode 2b is constituted by a divided electrode 2a. has been done. Split electrode 2a
is grounded via the variable capacitor 12, and the divided electrode 2b
is directly grounded. Ceramics are fitted between the divided electrodes 2a and 2b from the back side to electrically insulate them, and furthermore, a configuration is adopted in which the flow of gas for plasma processing is not changed. cathode gI3
The ceramic cover 9 has a circular planar shape in which the material to be etched can be placed.
The cathode electrode 3 is insulated from the wall of the plasma generation chamber, and a grounded high-frequency power source 4 and matching box 10 are connected to the cathode electrode 3. Further, the cathode electrode 3 can be rotated by a drive mechanism provided outside the plasma generation chamber 1. The high frequency power is efficiently supplied to the cathode electrode 3 by adjusting the matching box 10. Gas for plasma processing enters the plasma generation chamber 1 from supply equipment (not shown) through a supply pipe 7, is exhausted from an exhaust port 8, and the gas pressure in the plasma generation chamber 1 is adjusted by an exhaust valve (not shown). be able to.

Next, a case of etching will be explained as a specific example of plasma processing.

First, etching gas was supplied from the gas supply pipe 7 to set the plasma generation chamber 1 at a set pressure of 5 x 10-2 Torr, and then high-frequency power of 13.56 MHz was applied to the cathode electrode 3 to adjust the matching box. to generate plasma. The etching gas supplied from the gas supply pipe 7 is CF.
At step 4, the plasma is uniformly supplied from the supply equipment to the plasma generation chamber through the supply pipe 7 via a valve (not shown). The etching gas thus supplied is excited in the plasma and generates ions and radicals. The plasma generated by high frequency is strong around the electrode and weak in the center. Therefore, the divided anode electrode 2a was provided with a capacitance component controlled to an appropriate value by a variable capacitor 12 of maximum 500 pF, and the plasma intensity around the electrode was corrected. By doing so, the effect of the ion energy incident on the substrate can be made uniform, and the entire substrate can be etched uniformly.

As mentioned above, when the split electrode 2a is grounded via the variable capacitor 12, the matching of the high frequency power is shifted due to the capacitance component, and the same state as that in which the high frequency power input via the split electrode 2 becomes smaller is obtained. This makes it possible to reduce the plasma density in the region corresponding to the divided electrodes 2 and make the generated plasma density uniform between the electrodes 2 and 3.

Next, a specific example of etching processing using the apparatus having the configuration shown in FIG. 1 will be described below.

A disk-shaped support (Si wafer (6 inch diameter) or Corning 7059 glass (256 mm diameter) was used as the material to be etched.
Using amorphous silicon (n÷)M (thickness: 3000 mm) formed on the entire upper surface of The positions were aligned so that the centers of the surfaces coincided, and the arrangement as shown in FIG. 1 was obtained. Note that the interval between electrodes 2 and 3 was 50IIl111. Next, according to the above procedure, the plasma generation chamber is evacuated, CF4 gas is supplied from the gas supply pipe 7 at a flow rate of 255 (:CM), and the pressure inside the plasma generation chamber is reduced to 5 x 10-2 Tart.
And so. Here, a high frequency power of 300 W was applied from the high frequency power supply 4 through the matching box 10 to generate plasma and etching the amorphous silicon (NL) film.

When the capacitance of the variable capacitor is 100 pF, the etching rate is 18 at the portion corresponding to the divided electrode 2b.
0 people/min, 200 people/min in the part corresponding to the divided electrode 2a
person/min and was equalized between electrodes 2.3.

For comparison, etching was carried out under the same conditions as above, except that the apparatus shown in FIG. 2 having an undivided electrode as an anode electrode was used. Note that the arrangement of the amorphous silicon (n+) film between the electrodes is as shown in FIG. As a result, amorphous silicon (n”
) The etching speed in the central part of lli is 200 people/
The etching rate at the periphery was 250 people/min.

The case of etching has been explained above, but plasma C
When forming a film using the VD method, a film can be formed on the surface of the substrate 5 by supplying a film-forming gas from the gas supply pipe 7 . At this time, the thickness of the film deposited on the substrate 5 can be made uniform by controlling the plasma density in the same manner as in the above-described etching process.

In this manner, the apparatus of the present invention is applicable to processing performed using plasma and the energy of ions incident from the plasma.

In the above explanation, the positions of the divided electrodes are fixed and the plasma density is uniformly controlled by a correction circuit), but as shown in Figure 2, a movable mechanism is provided for each divided electrode to adjust the distance between the electrodes to the plasma density. The high portions may be wide, and the low density portions may be narrow, and may be used in place of or in conjunction with the impedance correction circuit. Although the divided electrode to which the impedance correction circuit is connected is the divided electrode 2a, the correction circuit can be connected only to the electrode 2b or to both electrodes 2a and 2b, if necessary.

In addition to the capacitor, the impedance correction circuit may be configured by using one or a combination of a coil and a resistor depending on the shape and size of the electrode, and the capacitor, coil, and resistor may be fixed types. It may also be a variable type. An example of the impedance correction circuit is shown in Fig. 4(a) to (d).
).

Note that the structure of the plasma generation chamber and the frequency of the high frequency power source are not limited to those in the above embodiments.

The shape of the electrode can be arbitrarily selected, such as rectangular or circular, as long as the plasma generation conditions are met.

In addition, the frequency of high-frequency power supply ranges from 100kHz to several tens of MHz.
You can arbitrarily choose up to.

Further, although alumina was used as the insulator between the divided electrodes in the above embodiment, quartz may be used in the case of film formation.

〔Effect of the invention〕

In the plasma processing apparatus of the present invention, the ground electrodes (anodes) of a pair of opposing electrodes to which high-frequency power for plasma generation is applied are divided, and impedance correction can be performed for each divided electrode.

According to the present invention, by adjusting the impedance of the divided electrodes as necessary, it is possible to partially adjust the impedance between the opposing electrodes, and as a result, the distribution of high frequency power input between these electrodes. can be made uniform, and a uniform generated plasma density can be obtained. Therefore, the action of ions and radicals incident on the material to be treated can be uniformly applied. Further, the influence of the generated ions and radicals on the material to be treated can be made uniform. As a result, plasma processing can be performed using optimal ion energy. For example, in the case of an etching process, the etching rate can be made uniform within the substrate, and the ion damage can also be made uniform. Furthermore, in the case of film formation, a homogeneous film can be formed.

In addition, in the etching process of a layer to be processed having an underlying layer such as an i-layer using the apparatus of the present invention, the underlying layer can be left with a uniform thickness. It is possible to improve variations in photocurrent and dark current of sensors, etc.

[Brief explanation of drawings]

1 and 2 are longitudinal sectional views showing essential parts of an example of a plasma processing apparatus of the present invention, FIG. 3 is a longitudinal sectional view showing essential parts of an example of a conventional plasma processing apparatus, and FIG. ) to (d) are diagrams showing examples of impedance correction circuits. 1: Plasma generation chamber 2 Near anode electrode 2a: Split electrode (periphery) 2b Two-split electrode (center) 3: Cathode electrode 4: High frequency power source 5: Substrate
6: Drive mechanism 7: Gas supply pipe 8
: Exhaust port 9: Ceramic cover 10 = Matching box 11: Ceramic 12: Variable capacitor 13.
14: Electrode movable mechanism

Claims (1)

[Claims] 1) In a plasma processing apparatus having a pair of opposing electrodes to which high frequency power for plasma generation is applied in a plasma generation chamber, a ground electrode (anode) side of the pair of opposing electrodes is divided into a plurality of parts. A plasma processing apparatus comprising electrodes and capable of impedance correction for each divided electrode. 2) The plasma processing apparatus according to claim 1, further comprising a circuit for correcting the impedance. 3) The plasma processing apparatus according to claim 1 or 2, wherein the impedance correction is performed by variably adjusting the distance between opposing electrodes for each divided electrode. 4) The plasma processing apparatus according to any one of claims 1 to 3, wherein each of the divided electrodes is insulated by an insulator. 5) The plasma processing apparatus according to any one of claims 1 to 4, comprising two or more of the pair of opposing electrodes, one or more of which has the divided electrode.